World in Ruin: This passive now increases your damage done with Flame and Poison attacks by 2/5%, rather than increasing your damage done with Area of Effect Flame attacks by 3/6% and reducing the cost of your Poison abilities by 12/25%.

It was changed to be increased damage, as the notes and the text says.

It was a pretty big sustain nerf, but the buff to combustion somewhat makes up for it and the 5% damage boost is nice.

The old passive was actually very limiting to the DK playstyle. Flame side only buffed AoE flame damage and the poison side only made the abilities cost less which was silly when poison status effects already gave stamina back.

Now Combustion gets buffed so you don't really need the reduced poison costs, all your poison abilities you do use hit harder, and you can with the right build perform just as well if not better. And a poison status effect stacking build is going to hit pretty hard all things considered since the status effect damage is getting buffed by 50% on top of the 5% more poison damage.